Although there has recently been much research on the interactions and activity regarding the growth and repair of certain tissues and cells, there has been little to no research on the effect of electric and/or electromagnetic fields on stem cells and the role that such stimulated cells might have on the growth and repair of bone, cartilage, and other tissues. Such research may be useful in the development of new treatments for a variety of medical problems.
The BMP family of genes include growth factors that are important in the promotion of bone formation and maintenance, from proliferation of pre-osteoblasts, to differentiation of pre-osteoblasts to mature osteoblasts, and to maintenance of the osteoblast throughout its life span. Transforming growth factors (TGF-beta 1, 2 and 3) control many cellular functions including growth, proliferation and differentiation. Fibroblastic growth factor (FGF-2) has been shown to have a positive anabolic effect on bone formation in intact animals and to reduce bone loss in experimental models of osteoporosis. FGF-2 (also termed basic fibroblastic growth or bFGF) stimulates bone formation, decreases osteoclast surfaces, and induces new bone spicules within the marrow cavity of bone.
Thus, up-regulation of the genes discussed above would be useful in the treatment of the disease commonly known as osteoporosis, where bone demineralizes and becomes abnormally rarefied. In osteoporosis, bone resorption exceeds bone formation, leading to bone weakening and possible vertebral body fracture and collapse. While osteoporosis is generally thought to afflict the elderly, certain types of osteoporosis may affect persons of all ages whose bones are not subject to functional stress. In such cases, patients may experience a significant loss of cortical and cancellous bone during prolonged periods of immobilization. Elderly patients are known to experience bone loss due to disuse when immobilized after fracture of a bone, and such bone loss may ultimately lead to a secondary fracture in an already osteoporotic skeleton. Diminished bone density may lead not only to vertebrae collapse, but also to fractures of hips, lower arms, wrists, ankles as well as incapacitating pains. Alternative non-surgical therapies to induce bone formation in such diseases are needed.
Pulsed electromagnetic fields (PEMF) and capacitive coupling (CC) have been used widely to treat nonhealing fractures (nonunion) and related problems in bone healing since approval by the Food and Drug Administration in 1979. The original basis for the trial of this form of therapy was the observation that physical stress on bone causes the appearance of tiny electric currents that, along with mechanical strain, were thought to be the mechanisms underlying transduction of the physical stresses into a signal that promotes bone formation. Along with direct electric field stimulation that was successful in the treatment of nonunion, noninvasive technologies using PEMF and capacitive coupling (where the electrodes are placed on the skin in the treatment zone) were also found to be effective. PEMFs generate small, induced currents (Faraday currents) in the highly-conductive extracellular fluid, while capacitive coupling directly causes currents in the tissues; both PEMFs and CC thereby mimic endogenous electrical currents.
The endogenous electrical currents, originally thought to be due to phenomena occurring at the surface of crystals in the bone, have been shown to be due primarily to movement of fluid containing electrolytes in channels of the bone containing organic constituents with fixed negative charges, generating what are called “streaming potentials.” Studies of electrical phenomena in bone have demonstrated a mechanical-electrical transduction mechanism that appears when bone is mechanically compressed, causing movement of fluid and electrolytes over the surface of fixed negative charges on the surface of bone cells, thus producing streaming potentials. These electrical potentials serve a purpose in bone, and, along with mechanical strain, lead to signal transduction that is capable of stimulating bone cell synthesis of a calcifiable matrix, and, hence, the formation of bone.
It was reported in 1996 by the present inventor and others that a cyclic biaxial 0.17% mechanical strain produces a significant increase in TGF-β1 mRNA in cultured MC3T3-E1 bone cells in a Cooper dish (Brighton et al., Biochem. Biophys. Res. Commun. 229: 449-453, 1996). Several significant studies followed in 1997. In one study it was reported that the same cyclic biaxial 0.17% mechanical strain produced a significant increase in PDGF-A mRNA in similar bone cells (Brighton et al., Biochem. Biophys. Res. Commun. 43: 339-346, 1997). It was also reported that a 60 kHz capacitively coupled electric field of 20 mV/cm produced a significant increase in TGF-β1 in similar bone cells in a Cooper dish (Brighton et al., Biochem. Biophys. Res. Commun. 237: 225-229, 1997). It has also been reported that chondrocyte matrix genes and proteins can be up-regulated by specific and selective electric fields (Wang, W., Wang, Z., Zhang, G., Clark, C. C., and Brighton, C. T., Clin. Orthp. and Related Res., 427S: S163-173, 2004; Brighton, C. T., Wang, W., and Clark, CC, Biochem. Biophys. Res. Commun., 342: 556-561, 2006). Further, it has been shown that the gene expression of bone morphogenetic proteins (BMPs) can also be up-regulated by specific and selective electric fields that differ from the electric fields in various signal aspects from those signals that are specific and selective for articular cartilage (Wang, Z., Clark, C. C. and Brighton, C. T., J. Bone Joint Surg., 88: 1053-1065, 2006).
In U.S. Pat. No. 7,465,566 to the present inventor, methods were disclosed for determining the specific and selective electrical and electromagnetic signals for use in creating fields for regulating target genes of diseased or injured tissues. The present invention builds upon the techniques described therein by describing the method of regulating expression of the targeted genes in bone marrow stem cells. These genes belong to the BMP super family, and include BMP 2 and 4, FGF-2, and TGF-beta 1, 2, 3, alkaline phosphatase, and osteocalcin. Through application of a field generated by a specific and selective electrical and electromagnetic signal, the treatment of bone diseases and injuries including osteoporosis, osteopenia, osteonecrosis, bone defects, fresh fractures, fractures at risk, delayed union, nonunion, and as an adjunct in spinal fusion is described.